The present inventive concepts relate to the field of electronics, and more particularly, to integrated-circuit chips.
Integrated-circuit devices, such as semiconductor devices, can be classified into memory devices and logic devices. Memory devices store data and can be classified into volatile memory devices and nonvolatile memory devices. Volatile memory devices, for example, DRAM (Dynamic Random Access Memory) and SRAM (Static Random Access Memory), loses stored data when its power supply is interrupted (e.g., when the power is turned off). Nonvolatile memory devices, for example, PROM (programmable ROM), EPROM (erasable PROM), EEPROM (electrically EPROM), and Flash memory device, does not lose stored data even when its power supply interrupted. Next generation memory devices, for example, MRAM (magnetic random access memory) and PRAM (phase change random access memory), are recently being developed for high performance and low power consumption. Next generation memory devices include a material having different resistance values according to current and/or voltage applied thereto, and the resistance values are maintained even power supply is interrupted.